Mobility of chromium in inorganic oxides Spectroscopic fingerprinting of oxidation states and coordination environments

Abstract

The mobility of Cr ⁿ⁺ in inorganic oxides has been investigated by combined diffuse reflectance (DR)–EPR spectroscopies as a function of the Cr oxidation state, the type of inorganic oxide (silica, alumina and mordenite) and the environmental conditions (hydrated and dehydrated state). Cr ⁿ⁺ ions are mobile under hydrated and dehydrated conditions and Cr ⁿ⁺ preferentially migrates from silica to alumina and, to a lesser extent, to mordenite, although only a small amount of migration of Cr ⁿ⁺ is observed from alumina to mordenite and vice versa. The observed preference sequences are discussed in relation to the properties of the inorganic oxides.